1. Field of the Invention:
This invention relates to plastic tiles which are supported above a floor surface to provide a playing surface for sports such as basketball, tennis, and the like. More particularly, the present invention pertains to modular tiles of plastic composition which are interlocked to form a playing surface where sudden lateral forces are imposed during use, requiring both traction and safety.
2. Prior Art:
A wide variety of floor coverings have been developed for use as playing surfaces for athletic activities. For example, hardwood floors have long been recognized as beneficial for rebound properties and comfort, but difficult to maintain and expensive to construct. Playing floors have also been constructed of tiles cemented to a cement subsurface; however, such flooring is very unforgiving to a fallen athlete, and offers minimal safety benefits. Both wood and fixed tile or cement floors share a similar disadvantage in that they are not capable of absorbing lateral impact forces so common to sport activities which involve jumping, running and sudden changes in direction of movement.
Modular flooring has grown in popularity because of its versatility, but has nevertheless failed to meet all desirable criteria of athletic floors. Structurally, the modular tile is fabricated of plastic material and usually adopts a grid configuration wherein the tile surface is a cross pattern of grid surfaces with closely spaced support legs extending down from grid crossings. A variety of grid patterns has developed, providing unusual aesthetic appearance as well as functional response.
The present inventor has developed a number of different modular tile members incorporating special leg support structure, as well as surface variations. The following U.S. Patent is representative of the inventor's prior work: U.S. Pat. No. Des. 274,588. Other inventors have similarly adopted the conventional approach for modular tile member wherein a grid system is used as the playing surface. These are represented by J. P. M. Becker, et al U.S. Pat. No. 3,438,312; Ralph Ettlinger, Jr. U.S. Pat. No. 3,909,996; K. Anthony Menconi, U.S. Pat. No. 4,436,799; Raymond W. Leclerc, U.S. Pat. No. 4,008,548; Esko Nissinen, U.S. Pat. No. 4,167,599; Hans Kraayenhof, U.S. Pat. No. 4,226,064; and Chester E. Dekko, U.S. Pat. No. Des. 255,744.
It is noteworthy that none of the athletic playing floors utilizing modular plastic members has adopted a continuous flat surface, despite the inherent advantage of comfort as demonstrated by traditional hardwood floors. Instead, the grid configuration is used, leading to special design problems for enhancing traction and reducing risk of injury due to falls and other forms of contact at the floor surface. Indeed, the dozens of differing designs occurring in the prior art are in most cases the result of attempts to adapt the grid system with one or more advantages of the flat surface more traditionally used in sport flooring.
A major reason for avoidance of the preferable flat, continuous surface arises from the difficulty of fabricating and maintaining plastic tiles which will rest flush on the supporting floor surface without adhesive, despite changes in temperature and effects of extended use. U.S. Pat. No. 4,436,799 by Menconi et al discusses several of the more important limitations that dictated in favor of fabrication of grid systems. For example, maintaining the support legs in contact with the support surface is critical, but has been a problem. Temperature variations may cause the tile to buckle, lifting corners or edges and creating a safety hazard as well as limiting the effective use of the tile floor as a ball-contacting surface. Id. Col 1, lines 30-37.
Prior art techniques for dealing with this limitation have included use of expansion joints and crossing reinforcement members or stiffeners. Stretch installation techniques have been applied and refinement of compositions to reduce thermal coefficients of expansion have also been attempted. The historical difficulty of dealing with such problems for grid configurations further reinforces the fact that modular tiles having a continuous flat surface are of even greater likelihood to buckle and distort. A continuous surface of plastic has a much greater tendency to twist and buckle as the polymer experiences temperature variations. Consequently, the prior art is virtually barren of plastic tiles for athletic flooring which have a continuous, flat surface and are modular and interlocking in a recurring manner.